1. Field of the Invention
This invention relates to a guide indication method in an onboard navigator which performs a most optimum route guiding and route instruction for a vehicle, and relates particularly to a guide indication method in case one""s vehicle makes a U-turn ahead of one""s vehicle and passes again through the present position.
2. Description of the Related Art
Conventionally, for example, as shown in FIG. 5, when one""s vehicle M travels on a road 1 and enters a road 2 to proceed to a destination, it turns to the left, if an intersection 4 prohibits right-turn, thereby traveling on the road 3 in the direction of arrows. One""s vehicle then makes a U-turn at a U-turn spot 5 and travels again on a route returning to the intersection 4 and, thereafter, enters the road 2 to continue along the route to the destination.
In such a road traffic condition, the guide in an onboard (in-vehicle) navigator is to indicate the U-turn route by means of an arrow, a colored line, or the like, and a voice guidance is also made like xe2x80x9cU-turn route aheadxe2x80x9d, or the like.
In the conventional guide indication method, in a case where one""s vehicle passes through the U-turn route and returns to the original position as described above, a guide is made to the effect that the U-turn will be made ahead, but no indication will be given of returning to the original position.
In case of a map navigator, the fact of returning to the original position will be known if an entire view of the U-turn route is indicated. However, if the U-turn spot is far away, the map can be sometimes indicated only partially. In such a case, it is not known at all whether one""s vehicle returns to the original position or not. Therefore, the driver of one""s vehicle was obliged to take the trouble of following the guide of the onboard navigator to thereby return to the original position after passing through the far U-turn spot.
As an onboard navigator, aside from the above-described map navigator, there is known a so-called arrow navigator in which indication is made only by an arrow without indicating a map. In this kind of arrow navigator, there is indication of neither a U-turn route nor a character. The driver was therefore unable to avoid the trouble of following the guide of the arrow, and returning to the original position after passing through the far U-turn spot.
This invention has been made to solve the above-described kind of drawbacks and has an object of obtaining a guide indication method in an onboard navigator in which, when one""s vehicle makes a U-turn ahead of one""s vehicle and passes again through the present position, that information has to be reported.
A guide indication method in an onboard navigator according to this invention in which a route guide to a destination along a route set in advance is indicated on a display comprises the steps of: detecting, through route searching, a closest link in a departure place of one""s vehicle; and when a U-turn route link to come back by passing from the closest link through the U-turn route again to the closest link is detected, performing a U-turn guide, based on a signal of this detection, to an effect that a return is made to the present position after a U-turn.
Thus, when one""s vehicle passes again through the present position after making a U-turn ahead of one""s vehicle, a guide is made to that effect. Therefore, the driver is able to make a U-turn by utilizing an appropriate place on the way based on his/her own determination without taking the trouble of going all the way to the U-turn spot, thereby attaining an effect in that the driving along an unnecessary section can be omitted.
The guide indication method in an onboard navigator according to this invention is characterized in that the onboard navigator is a map navigator and that the U-turn guide is a character indication to the effect that a return is made to the present position after a U-turn.
Thus, when one""s vehicle passes again through the present position after making a U-turn ahead of one""s vehicle, that fact is reported to the driver by means of character indication. Therefore, there is an effect in that the driver is able to omit the driving along an unnecessary section.
The guide indication method in an onboard navigator according to this invention is characterized in that the onboard navigator is an arrow navigator and that the U-turn guide is made up of a mark showing a U-turn and a distance to return to the present position.
Thus, when one""s vehicle passes again through the present position after making a U-turn ahead of one""s vehicle, that fact is reported to the driver by means of the mark and the distance. In the arrow navigator, there is an effect in that the driver is able to omit the driving along an unnecessary section.
The guide indication method in an onboard navigator according to this invention is characterized in that the U-turn guide is a voice guide.
Thus, when one""s vehicle passes again through the present position after making a U-turn ahead of one""s vehicle, that fact is reported also in a voice. Therefore, there is an effect in that the confirmation of the U-turn guide becomes easier and that the driver is able to omit the driving along an unnecessary section.